Electroplating process



Patented Mar. 11, 1930 UNITED STATES PATENT OFFICE ROBERT BRACE PENN CRAWFORD, OF CHICAGO, ILLINOIS, AND ROY DIEIRICH SNYDER, OF HAZLETON, PENNSYLVANIA ELECTROPLA'IING- PROCESS No Drawing. Application filed November 26, 1921, Serial No. 517,895. Renewed January 23, 1930.

The present invention relates to an improved electroplating process whereby nonferrous metals, for example, an alloy of copper and nickel, are deposited on a base of metal, or other suitable material.

A particular object of this invention is to form a coating or skin for metals of a nickelcopper alloy that possesses all the advantages of the pure nickel coating, but which is less expensive to produce, and, due to its non-corrosive qualities forms a protective and lustrous homogeneous deposit on metal articles, such as pipes, conduits, valves, etc., that otherwise when subjected to the tarnishing influonce of the atmosphere and the corrosive effects of liquids, would deteriorate. The alloy deposit has properties resembling Monel metal.

The electrolytic bath employed for depositing the alloy upon non-ferrous metals is composed of the following ingredients in sub stantiall the pro ortions herein set forth:

Nicke sulfate NiSo .6H O),80 oz. (600 g.

per liter). Copper acetate (Cu(Ac) 2% oz. (20 g. per liter). Nickel acetate (NiAc 5 oz. (4.0 g. per liter). Sodium chloride (NaCl), 1% oz. (10 g. per liter).

The above named ingredients are mixed in about a gallon of water with one part in 2000 of white glue, or any other kind of glue, for example commercial liquid glue, the purpose of which is to act as an addition agent. The bath at ordinary room temperature has passed through it an electric current of approximately 2 amperes per square foot density on the cathode, and is allowed to age for about fourhours. The length of time that the current may pass will vary, dependent on the thickness of the deposit desired. In practicing the invention, current has been passed for about thirty (30) minutes on an average, giving a relatively thin plate which, while it would take a polish, would not be heavy enough for a protective coating. In applying protective coatings for which heavier plates are desired, we have run the current for three (3) or four (4) hours. Within certain limits it is immaterial for any given weight of plate whethor you use high current density, for short periods, or Whether you run for a long time at a low current density. F orinstance,at acurrent density of 0.5 amp/dm we get a deposit of .03 of a gram of copper nickel alloy on a 30 sq. cm. Platinum foil in thirty (30) minutes. On the same foil, at a current density of 2.0 amperes per square decimeter, We get .17 gm. deposit of copper nickel alloy in thirty (30) minutes. At a current density of 1.0 aInps/dm we get .18 gm. of copper nickel alloy deposited in one hour on the same electrode.

For plating iron and steel, the bath will be compounded of the following ingredients, mixed in about a gallon of water:

Nickel ammonium sulfate Nismmm 80 51-1 0),

13 oz. (97.5 g. per liter). Copper oxalate (CuC O oz. (3.75 g.per liter) Boricacid (H 30 2 oz. (20 g. per liter). Nickel chlorlde (NlGl 1 oz. (7.5 g. per liter), and enough ammonium hydroxide (NH OI-I) to dissolve the copper oxalate. In some cases we may add about one part in 2000 of glue, as stated above.

This bath has passed through it an electric current of approximately five amperes per square foot density on the cathode, and is allowed to age for about four hours. As hereso inbefore stated, the length of time that the current is allowed to pass will depend on the thickness of the plate or coating desired.

While we have selected copper salts of organic acids for use in the electrolytes; we do not wish to be limited thereby, as salts of other acids are operative.

The object to be coated or plated in these baths form the cathode or negative electrode, While the copper-nickel alloy forms the anode so or positive electrode. Several anodes may be used. The object to be coated is slowly drawn through the bath between the copper-nickel alloy, that is, the anodes. Standard types of electroplating machines may also be used. The percentage of the copper deposit on the metal will, of course, be affected by the composition of the bath, the temperature, the degree of agitation, and current density.

The composition of the bath, the temperinstances.

ature, the degree of agitation and the current density all aflect the percentage of copper 1n the deposit. By aging the solution or several hours under a given set of conditlons, the composition of the bath so varies that the percentage of copper in the plate is the same as the percentage of copper in theanode. Hence, b suitable investigation corresponding equili rium values for concentration, current density, a itation and temperature can be determine in advance and the time of aging reduced.

The character of the deposit from any given bath is influenced only by the acidity or asicity of the solution. Ifthe current efliciency is greater atthe anode than at the cathode, the solution grows basic, and this effect can be obviated by allowing the dilute sulfuric or acetic acid to flow in the agitated electrolyte drop by dro at a calibrated rate to keep the acidity (hy ro en-ion concentration) constant or normal If the current efliciencyl at the cathode is higher than at the anode, t e solution grows acidic. To remedy this, the solution is preferably drawn off from the top and filtered throu h a predetermined mixture of copper and nic el hydroxid, thereby dissolving some of the hydroxids, and returned to the electrolyte thus keeping the hydrogen-ion concentration constant. As all alloys have different anodic current efiiciencies, no specific directions can be given. Cast alloys have higher efficiencies as'anodes than rolled or cold worked ones. The anodic current efliciency can be varied by the addition of chlorides to the bath, for example, nickel chloride, or sodium chloride, although more than one and one-third ounces per gallon effects the quality of the deposit.

A desired mixture of copper and nickel hydroxids may be obtained by adding an excess of sodium hydroxid to a satisfactorily mixed and aged normal electrolyte, and boiling until the ammonia fumes are ex lled. The precipitate is filtered and washe The mixture ma also be obtained by precipitating any desired solution of copper and nickel salts.

For commercial operation the balancing of anodic and cathodic current efliciencies is superior to the corrections for acidity or basicity mentioned above. This balancing can easily be accomplished by the following methl od: Choose the copper nickel alloy it is desired to plate; 'if commercially use cast anodes of this allo racticable; add enough chloride to make t e average anodic current efiiciency equal to the average cathodic efiiciency. Usually sodium chloride is added, although nickel chloride is preferable in many The iron present in many copper-nickel alloys does not materially interfere with the efiective operation of the bath, but it can be removed by eirc the electrolyte comprising sulphates,

through a precipitating bath, adding basic nickel carbonate and filtering, if its presence lmpairs the quality of the deposit on the metal.

It is to be understood that the proportions of the ingredients above set forth may be 'varied to a considerable extent and still be within the scope of the present invention.

We claim:

1. An electrolyte for electrodepositing an alloy of copper and nickel, which comprises nickel ammonium sulfate, copper oxalate, boric acid, nickel chloride, ammonium hydroxid, and water.

2. The method of electrodepositing a copper-nickel alloy upon a cathode, which comprises passing an electric current from anodes containing copper and nickel, to a cathode,

through an electrolyte containing a nickel salt composed of one of a group comprising sulphates, acetates and chlorides, a copper salt of an acid which dissociates very slightly, a soluble chloride, and water.

3. The method of electrodepositing a copper-nickel alloy upon a cathode, which comprises passing an electric current from an anode containing copper and nickel to a cathode, through an electrolyte containing a nickel salt composed of one of a group comprising sulphates, acetates and chlorides and a copper salt of 'an acid group, comprising acetates and oxalates, and aging the solution with an anode having the composition it is desired to deposit.

4. The method of electrodepositing a copper-nickel alloy upon a cathode, which comprises passing an electric current from an anode containing copper and nickel to a cathode through an electrolyte containing a nickel salt composed of one of a roup comprising sulphates, acetates and ch orides and a copper salt of the acid (group, comprising oxalates and acetates, an maintaining the neutral condition of the electrolyte by correcting its acidity during use.

5. An electrolyte for electrodepositing an alloy of copper and nickel which comprises a nickel salt composed of one of a group comprising sulphates, acetates and chlorides, a copper salt. of a group including acetates and oxalates, a soluble chloride and water.

6. An electrolyte for electrodepositing an alloy of copper and nickel which comprises a nickel salt composed of one of a group comprising sulphates, acetates and chlorides, a copper salt of a group including acetates and oxalates, a soluble chloride, ammonium hydroxid and water.

7. An electrolyte for electrodepositing an alloy of copper and nickel, which comprises a nickel salt composed of one of a group acetates and chlorides, a copper salt of a roup including acetates and oxalates, a solu le chloride, ammonium hydroxid, boric acid and water.

8. An electrolyte for electrodepositing an alloy of copper and nickel, which comprises a nickelsalt composed of one of a group comprising sulphates, acetates and chlorides, a copper salt of a group including acetates and oxalates, a soluble chloride, ammonium hydroxid, boric acid, glue and water.

9. An electrolyte for electrodepositing an alloy of copper and nickel, which comprises two nickel salts from a group comprising sulphates, acetates and chlorides, one of such salts being in excess of the other, a copper salt of an acid group comprising oxalates and acetates, a soluble chloride and water.

10. An electrolyte for electrodepositing an alloy of copper and nickel, which comprises a nickel sulphate and a nickel salt from a group "comprising chlorides and acetates, a

copper salt of an acid group comprising'oxalates and acetates, a soluble chloride and water.

11. An electrolyte for electrodepositing an alloy of copper and nickel, which comprises ammonium sulphate, nickel chloride, a copper salt of the acid group comprising oxalates and acetates, boric acid, ammonium hydroxid and water. 12. An electrolyte for electrodepositing an alloy of copper and nickel, which comprises a nickel sulphate, a nickel salt of a group comprising chlorides and acetates, copper acetate, sodium chloride, glue and water.

In testimony whereof we have hereunto set our hands.

ROBERT BRACE PENN CRAWFORD. ROY DIETRICH SNYDER. 

